This project involves clinical and immunologic studies of humans infected with the intestinal nematode Strongyloides stercoralis, and parallel studies in an experimental host, the patas monkey. This parasite deserves special investigative attention because it often goes undiagnosed, it can be fatal in immunosuppressed individuals, and has unusual biological properties. During maintenance of the parasite in the monkey during last year we evaluated and found once again that the immediate hypersensitivity skin test elicited nonspecific reactions in the monkey and was not useable. One infected animal was repeatedly exposed to infective larvae to obtain a hyperimmune serum. Most effort on the project was given to analysis of somatic and excretory-secretory (E/S) antigens prepared from infective (L3) larvae. Only antigens that react with IgG from pooled patients' sera can be identified by immunoblotting. Repeated attempts to detect antigens by Western blot, as well as dot blot, that react with IgE have been negative. Yet we believe that allergic reactions to strongyloides antigens (as assayed by in-vitro histamine release) are mediated by IgE. Support for this comes from an experiment in which heating serum of patients before in- vitro passive sensitization of donor basophils ablated ability of antigen to release histamine. Additional probes to identify and characterize the various larval antigens are being developed-- some fractions show protease activity and polyvalent rabbit antisera that react with parasite antigens have been raised. Several patients with strongyliodiasis have been encountered who have antibody evidence of infection with the retrovirus HTLV-1.